Squawk codes: what each one means.

What a squawk code is

A squawk code is the four-digit number a pilot sets on the aircraft’s transponder so that air traffic control radar can tell one aircraft from another. “Squawk” is the controller’s verb: “squawk 4521” means “set 4521”. Every digit runs from 0 to 7, which gives 8 × 8 × 8 × 8 = 4,096 possible codes, the “4,096 discrete codes” the FAA’s Aeronautical Information Manual (AIM) refers to. A controller hands most of these out one at a time. A short list has a fixed meaning that every pilot and controller is expected to know, and that list is what the table above shows. Each row names the rule that backs it.

The three emergency codes

7700, 7600 and 7500 are the codes with the same core meaning in the US and in EU rules. 7700 is an emergency. The AIM (6-2-2) says a pilot in a distress or urgency condition who wants to alert a ground radar facility should squawk Mode 3/A code 7700 with altitude reporting and then immediately establish communications with ATC, and keep squawking 7700 because the aircraft might not be in radar coverage. EU rule SERA.13005 says to select 7700 unless ATC has already directed a specific code, and allows 7700 even then if there is specific reason to believe it is the best course.

7600 is lost radio. AIM 6-4-2 tells a pilot who loses two-way radio capability to set code 7600 and warns that the aircraft may be outside radar coverage. SERA.13005 gives the same meaning. 7500 is unlawful interference. The FAA’s controller manual (JO 7110.65, 5-2-5) tells a controller who sees 7500 to apply the hijacked-aircraft procedures, and the AIM adds that only a non-discrete 7500 is decoded as the hijack code. SERA is worded differently: the pilot should attempt to select 7500, and “if circumstances so warrant, Code 7700 should be used instead”.

VFR codes: 1200 and its US variants

In the United States, 1200 is the code for VFR aircraft that have no other code. The AIM says that unless ATC instructs otherwise, a VFR aircraft sets 1200 regardless of altitude, and the controller manual has controllers tell an aircraft whose radar service has ended to “squawk VFR” or “squawk 1200”. The FAA lists a few replacements for it: 1202 for VFR gliders, 1203 for the lead aircraft of a VFR formation that is not talking to ATC (the others squawk standby), 1255 for firefighting aircraft working a designated fire area, and 1277 for authorized USAF or USCG search and rescue flights when advised. Controllers are told to keep monitoring 1200, 1202, 1203, 1255 and 1277 outside Class A airspace.

Europe: 7000 and 2000

The EU rule on Mode A code setting (SERA.13005(b)) has three steps in order: use the code ATS gives you; if there is no instruction on code setting, select 2000 or another code the competent authority prescribes; and when you are not receiving air traffic services, select 7000 to improve detection by suitably equipped aircraft, unless the state prescribes otherwise. 7000 is therefore what many European VFR pilots set when flying without a service, but the rule gives each state room to say differently, so the AIP of the country you are in is the final word.

Worked example (hypothetical)

A pilot flying VFR in the US has been using flight following on a discrete code. When the controller says “radar service terminated, squawk VFR”, the pilot sets 1200 and changes frequency. An hour later a different hypothetical pilot in an IFR flight loses both radios. Under AIM 6-4-2 that pilot sets 7600 and then follows the lost-communications procedures, which are a separate topic from the code. A third hypothetical pilot, flying in an EU state with no air traffic service, sets 7000 unless that state’s rules say otherwise. In all three cases the code is a signal to a controller, not a replacement for a radio call.

Edge cases and common mistakes

• Dialling through an alarm code. The AIM says that when changing codes you should avoid selecting 7500, 7600 or 7700 by accident, because it causes momentary false alarms. Its example: going from 2700 to 7200, switch to 2200 first, not through 7700.
• The whole 7600 and 7700 series. The AIM says every discrete code from 7600-7677 and 7700-7777 triggers special indicators at automated facilities, which is why the lookup warns about codes in those ranges.
• IDENT. Both the AIM and SERA.13001 say to use the IDENT feature only when ATC asks.
• Civil use of 7777. Never. The AIM reserves it for military interceptor operations.
• Assuming 1200 is universal. It is a US assignment in the sources read here; the EU text we read does not use it.

Who this is for

Student and private pilots revising the codes they are expected to know, people watching flight-tracking software who want to know what a 7700 alert means, writers and flight-sim users who want the real rule behind a code, and anyone who heard “squawk” on the radio and wondered.

What this does not cover

• Canada, the UK, Australia and other states: their national code assignments are not in the sources we read, so they are not listed.
• The full FAA National Beacon Code Allocation Plan (JO 7110.66) and the thousands of codes ATC assigns locally.
• What to do after setting 7600 or 7700; follow the AIM, your operating rules and ATC instructions.
• The aircraft’s 24-bit Mode S address, which is a different number (see the N-number to ICAO hex converter).
• Anything real-time: this page reads no radar, tracker or registry data.

Codes at a glance